This means we need the registrar(<programName>) dbd file entry only
in case an IOC shell is actually used.

* seq internal type definitions (seqPvt.h):
  - grouped struct members according to quasi-static vs. dynamic
  - factored out struct assigned_channel from struct channel
  - removed struct queue_entry, use new seq_queue module instead
  - added stuff needed for safe mode to struct state_set_control_block:
    USER_VAR pointer, an array of dirty flags (one per channel)
* refactored and simplified thread initialization and shutdown,
  removed the death1/2/3/4 cruft
* removed auxiliary thread (and related types); Jeff Hill confirmed
  that this is redundant if CA is used with preemptive callbacks enabled
* removed all remaining global variables, except in seqCommands where
  they get initialized before multithreading starts; pvSys now gets
  initialized inside seqAddProg (with a global mutex taken)
* conceptually separate program (which gets registered before
  multithreading starts) and running instance, add instance number
  to the latter to distinguish them (in addition to thread id)
* completed implementation of safe mode:
  - additions to pvPut, pvGet, pvGetQ for anonymous pvs
  - anonymous pvs now work exactly as named ones
* re-worked SYNC/ASYNC pvPut/pvGet, so that they work as documented
* adapted documentation

Specifically:
- replaced members of type long with more specific types
  (mostly unsigned or aliases thereof), see previous patch
  with similar changes to the API; checked everywhere with
  extra warnings enabled that there are no inconsistencies
- also renamed some structs in internal header seqPvt.h
- made some string members const, according changes in c files
  mostly to seq_mac.c

This may be viewed as old-fashioned but at least it is consistent now,
whereas formerly it was a wild mixture of local and global includes.
We may later decide to revert this but then it will be done uniformly
for all source files, too.

This avoids a race condition when creating the global progList (in
seq_prog.c) and also avoids code duplication. The global variables in
seq_prog.c have been removed. Instead we extend the sequencer program
list in seqCommands.c so that for each program it also stores a list
of program instances, each one protected by a mutex. Access to this
list is restricted to a single generic traversal procedure which
automatically applies the lock around each call to the supplied
traversee. Since the program list in seqCommands.c is created before
multithreading starts there is no race condition.

Also added an int return value to the traversees, to indicate whether
traversal is supposed to stop (TRUE) or continue (FALSE).

sequencer commands and programs.  Remove the conditional compilation tests
around the code that uses constructors.